So after we have done the pressure test, we have some important data to use in further load development. What is important is that we need to go under our rifle maximum charge for two reasons. First reason is because in hot weather we don’t want to go over pressure and second reason is because the cases will last longer.
If you haven’t read the first part you can find it here: Load development part I – pressure test
Using pressure test data
In the pressure test we have found our rifle maximum and some loads that had small vertical spread.
Loads 7 (26,4gr), 8(26,6gr) and 9(26,8gr) will be used as start point. Now I have decided to do 7 different loads. So I made 0,1gr increments and started 0,1gr under load 7 and 0,1gr over load 9. For this test lower the increments on half of pressure test. So I had 0,2gr increments on pressure tests and now I have 0,1gr increments.
Loading for testing charges
This loads have been previously tested in my rifle and are over book maximum so don’t use them without first doing the pressure test! Always start at book minimum! I don’t take any responsibility for using this loads in your rifle!!!
All other things like COAL and primers stay the same. Let me first explain what we will do in this test. We will shoot our charges in 3 targets and we will repeat the test twice. Because we don’t want to miss the target and for barrel fouling we have 12 shots of load 1. 6 for testing and 6 for barrel fouling and sight-in. And we will do the test on 2 separate days so we can use 3 foulers (you can load more if you find it necessary) each day. After sighting-in we start shooting test targets. First day we shoot in 1st target 7 shots. Each shot with a different charge so load 1,2,3,4,5,6 and 7. Then in 2nd target again 7 shots. Now loads from 7-1. And on the 3rd target again 7 shots with loads from 1-7. On the second target we shoot loads from 7-1 to minimize barrel temperature effects. I suggest to place the targets at the distance between 200-400m to have a better result. At 100m the grouping might be a little bit to tight to get good results. But don’t forget that you have to know which shot is which so you need to see the shots and mark them in the log book. If you will not be able to see the shot in the target you will have to walk downrange and check it.
On the left it is the data from day one and on the right from day 2. On both days I wasn’t able to get good readings from my chronograph because of strong wind and sun. P.S. on day 1 my wife wrote down the data, I guess you can see it…
Left targets are from day 1 and right targets from day 2
When we finish shooting we have 2 groups of targets to collect the data from. For do it easily I take my log book and I paint 7 vertical lines on one paper and another 7 on the other paper and now I mark shots 1-7 on the appropriate line from 3 targets from day 1 and on the other paper from day 2 targets. By doing this I can see vertical dispersion of my loads. What I am looking for is the smallest vertical dispersion possible.
Now that we have marked all shots we can see which loads performed best. On both days I have the smallest vertical dispersion with load number 7 so this will be one start point for further load development. Than I have under 1/2 moa vertical dispersion on load 6 on both days so this will be the second start point and on the second day I have a small vertical spread also with load 2. So I will take this as the third starting point.
I have done the charge test at the range of 210m and all targets have vertical dispersion of 1 moa or better which is really good if we consider that groups are from 7 different loads. What I find important is also to do all load development from the actual position that will be used for shooting. Don’t do the load development from a bench with all sorts of front rests if you will later use the rifle for hunting and vice versa. I do all my load development from a prone position and with a bipod. Actually this load is for Fclass competitions where I will shoot the F/tr class with the exact same position and with the bipod.
You can find the discussion about this article on EU-LRH forum.